Temozolomide, an alkylating drug, is marketed in the U.S. as TEMODAR® for the treatment of adult patients with newly diagnosed glioblastoma multiforme (GBM) concomitantly with radiotherapy and then as maintenance treatment. Temozolomide is also marketed for the treatment of refractory anaplastic astrocytoma patients who have experienced disease progression on a drug regimen containing nitrosourea and procarbazine. Temozolomide is currently available in the form of oral capsules and a vial for injection.
A typical regimen for patients with GBM taking temolozomide consists of two phases, a concomitant phase followed by a maintenance phase, both of which are weight-based dosing regimens. During the concomitant phase, the patient receives an oral administration of 75 mg/m2 of temolozomide daily for 42 days concomitant with focal radiotherapy (60 Gy administered in 30 fractions). This corresponds to approximately 140 mg for a patient having a body surface area (BSA) between 1.8 and 1.9 m2. Four weeks after completing the concomitant phase, the patient receives 6 cycles of maintenance treatment. In the first maintenance cycle, temozolomide is administered at 150 mg/m2 (approximately 280 mg for a patient having a BSA between 1.8 and 1.9 m2) once daily for five days followed by 23 days without treatment. The dosage may be escalated to 200 mg/m2 (approximately 360 mg for a patient having a BSA between 1.8 and 1.9 ml) for the first 5 days of each subsequent cycle. Weight-based dosing using oral tablets and capsules is complex, and inadvertent overdose can be fatal. Capsules and tablets only come in discrete amounts, often requiring patients to self-administer various combinations of different dosage strengths of a medicine to obtain the desired dose. Temodar capsules, for instance, are available in six dosage strengths (5, 20, 100, 140, 180 and 250 mg). In many circumstances, doctors have to round the dose to fit the capsule strengths available. These factors result in a high risk for dispensing errors and administration errors, which have resulted in deaths in the past. One study found that 47% of medication errors were patient and care-giver administration errors, while 29% were dispensing errors. See, e.g., Letarte et al., J. Neurooncol., 120(1), 111-1155, 2014 (analyzing reported medication errors involving oral capsules of temozolomide).
Many weight-based dosed medications avoid the need to combine various dosage strengths of a medicine by providing them as oral or intravenous liquids. Intravenous liquids are inconvenient and undesirable for self-administration. Oral liquid forms of temozolomide are undesirable as temozolomide is dangerous on skin contact, being classified for both skin corrosion/irritation and eye irritation in category 2. In view of these safety issues, the prescribing information for Temodar provides that Temodar capsules are to be swallowed whole, and not chewed, opened, or split. The prescribing information further provides that if Temodar capsules are accidentally opened or damaged, the user should be careful not to inhale the powder from the capsules or get the powder on his or her skin or mucous membranes (for example, nose or mouth). If contact with any of these areas happens, the user is to flush the area with water. There is therefore a need for convenient, safe, and reliable methods for titrating and dosing of temozolomide.